U.S. patent application number 10/371501 was filed with the patent office on 2003-08-07 for optical element holding device.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Nishikawa, Jin.
Application Number | 20030147155 10/371501 |
Document ID | / |
Family ID | 18744847 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030147155 |
Kind Code |
A1 |
Nishikawa, Jin |
August 7, 2003 |
Optical element holding device
Abstract
An optical element holding device includes a holder having a
bearing surface and a clamping member for holding a flange of a
lens, and a frame coupled to a barrel. The holder holds the lens
such that its optical axis AX' is oriented in the horizontal
direction. The holder is arranged such that a plane P1 passing
through its holding position and extending in a direction
intersecting the optical axis of the lens substantially passes
through the center of gravity Gc of the lens. The holder thus
arranged stably holds the lens while preventing a moment of
rotation from being produced, restrains deformation of optical
surfaces of the lens, and maintains satisfactory optical
performance.
Inventors: |
Nishikawa, Jin;
(Kumagaya-shi, JP) |
Correspondence
Address: |
SYNNESTVEDT & LECHNER, LLP
2600 ARAMARK TOWER
1101 MARKET STREET
PHILADELPHIA
PA
191072950
|
Assignee: |
Nikon Corporation
Chiyoda-ku
JP
|
Family ID: |
18744847 |
Appl. No.: |
10/371501 |
Filed: |
February 21, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10371501 |
Feb 21, 2003 |
|
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|
PCT/JP01/07214 |
Aug 23, 2001 |
|
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Current U.S.
Class: |
359/819 |
Current CPC
Class: |
G02B 13/143 20130101;
G02B 7/022 20130101; G02B 7/026 20130101; G03F 7/70825 20130101;
G02B 17/08 20130101; G02B 17/0892 20130101 |
Class at
Publication: |
359/819 |
International
Class: |
G02B 007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2000 |
JP |
2000-256203 |
Claims
What is claimed is:
1. A device for holding an optical element having a periphery and
an optical axis, the device comprising: a plurality of holders
communicated with the periphery of the optical element and holding
the periphery of the optical element, each holder being configured
to clamp the optical element such that the optical axis of the
optical element is oriented in the horizontal direction or in an
oblique direction relative to horizontal, and such that a plane
passing through a position for holding the optical element and
extending in a direction intersecting the optical axis of the
optical element substantially passes through the center of gravity
of the optical element.
2. The device according to claim 1, wherein at least three of the
holders are arranged at substantially equal intervals along the
periphery of the optical element.
3. The device according to claim 2, wherein the holders are
arranged at positions rotationally symmetric to the optical axis of
the optical element.
4. The device according to claim 2 or 3, wherein the holders are
arranged at positions symmetric to a plane which includes the
optical axis of the optical element and extends in the gravity
direction.
5. The device according to claim 1, wherein the position for
holding the optical element includes a flange formed on the
periphery of the optical element, and wherein each holder clamps
the flange.
6. The device according to claim 5, wherein the plane is positioned
between flange surfaces parallel with each other, the flange
surfaces defining the flange.
7. The device according to claim 6, wherein the plane is positioned
halfway between the flange surfaces.
8. The device according to claim 1, wherein the optical element is
a reflective mirror.
9. A barrel for holding optical elements in which at least one
optical element includes a periphery and an optical axis, the
barrel comprising: a holder communicated with the periphery of at
least one optical element and holding the periphery of the at least
one optical element, the holder being configured to hold the at
least one optical element such that the optical axis of the at
least one optical element is oriented in the horizontal direction
or in an oblique direction relative to horizontal, and such that a
plane passing through a position for holding the at least one
optical element and extending in a direction intersecting the
optical axis of the at least one optical element substantially
passes through the center of gravity of the at least one optical
element.
10. An exposure apparatus for transferring a pattern formed on a
mask to a substrate, the exposure apparatus comprising: a
projection optical system through which the image of the pattern
formed on the mask is transferred onto the substrate, the
projection optical system including a barrel and a plurality of
optical elements held in the barrel, wherein at least one optical
element includes a periphery and an optical axis, the barrel having
an optical element holding device which holds the at least one
optical element, the optical element holding device including a
holder communicated with the periphery of the at least one optical
element and holding the periphery of the at least one optical
element, the holder being configured to hold the optical element
such that the optical axis of the optical element is oriented in
the horizontal direction or in an oblique direction relative to
horizontal, and such that a plane passing through a position for
holding the optical element and extending in a direction
intersecting the optical axis of the optical element substantially
passes through the center of gravity of the optical element.
11. A method of manufacturing a micro-device characterized by
manufacturing the micro-device using the exposure apparatus
according to claim 10.
Description
RELATED APPLICATION
[0001] This application is a continuation of PCT application number
PCT/JP01/07214 filed on Aug. 23, 2001.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an optical element holding
device for holding an optical element, and more particularly to an
optical element holding device for holding an optical element
placed in a light path of exposure light in an exposure apparatus
for use in a photolithography step in a process for manufacturing
microdevices, such as semiconductor devices, liquid crystal display
devices, imaging devices, and thin-film magnetic heads, or masks,
such as reticles and photomasks. The present invention also relates
to a barrel which contains the optical element holding device, and
an exposure apparatus which has the barrel. The present invention
further relates to a method of manufacturing a microdevice using
the exposure apparatus.
[0003] Known as this type of optical element holding device is what
is configured to hold a lens 81A as an optical element such that
its optical axis AX is oriented in the vertical direction (gravity
direction), for example, as illustrated in FIGS. 16 and 17. In this
prior art configuration, a frame 82 for holding the lens 81A is
formed in an annular shape. The frame 82 is formed with three
bearing surfaces 83 formed on the inner peripheral surface at equal
angular intervals, such that a flange 81a formed along the outer
periphery of the lens 81A is supported on these bearing surfaces
83.
[0004] Three clamping members 84 are attached on the top surface of
the frame 82 in correspondence to the respective bearing surfaces
83 at equal angular intervals with bolts 86 which are screwed into
screw holes 85 on the frame 82. These bolts 86 are fastened to
clamp the flange 81a of the lens 81A between the respective
clamping members 84 and the bearing surfaces 83, thereby holding
the lens 81A at a predetermined position in the frame 82.
[0005] However, in a catadioptric projection optical system or the
like, for example, the lens 81A may be placed such that the optical
axis AX is oriented in the horizontal direction or in an oblique
direction which inclines at a predetermined angle with respect to
the horizontal direction. In such a configuration, the gravity
direction Gd of the lens 81A does not match the optical axis AX but
is oriented in a direction which intersects the optical axis AX.
Consequently, the optical system in this configuration causes the
following problems.
[0006] Specifically, when the flange 81a of the lens 81A is held by
clamping the same between the three clamping members 84 and the
bearing surfaces 83, the clamping position (a plane P1 including
three holding positions) separated from the center of gravity Gc of
the lens 81A causes a moment of rotation M1 which is generated by
the gravity of the lens 81A with a fulcrum F1 located at the
intersection of the clamping position with the optical axis AX.
This results in deformed lens surfaces and mirror surface, giving
rise to a problem of exacerbated optical characteristics of the
lens 81A and/or mirror, and an increase in various aberrations,
such as wave front aberration and spherical aberration.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide an
optical element holding device which is capable of stably holding
an optical element while limiting the moment produced in the
optical element to restrain deformed optical surfaces of the
optical element, thereby maintaining satisfactory optical
performance.
[0008] The present invention provides a device for holding an
optical element. The device includes a holder which holds the
periphery of the optical element. The holder is configured to hold
the optical element such that the optical axis of the optical
element is oriented in the horizontal direction or in an oblique
direction relative to horizontal, and such that a plane passing
through a position for holding the optical element and extending in
a direction intersecting the optical axis of the optical element
substantially passes through the center of gravity of the optical
element.
[0009] Other aspects and advantages of the present invention will
become apparent from the following description, taken in
conjunction with the accompanying drawings, illustrating by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The features of the present invention that are believed to
be novel are set forth with particularity in the appended claims.
The invention, together with objects and advantages thereof, may
best be understood by reference to the following description of the
presently preferred embodiments together with the accompanying
drawings in which:
[0011] FIG. 1 is a diagram schematically illustrating the
configuration of a whole exposure apparatus;
[0012] FIG. 2 is a diagram schematically illustrating the
configuration of a projection optical system and its surroundings
in FIG. 1;
[0013] FIG. 3 is a cross-sectional view illustrating an optical
element holding device according to a first embodiment of the
present invention;
[0014] FIG. 4 is a side view of the optical element holding device
in FIG. 3;
[0015] FIG. 5 is an exploded perspective view of the optical
element holding device in FIG. 3;
[0016] FIG. 6 is a cross-sectional view illustrating an optical
element holding device according to a second embodiment of the
present invention;
[0017] FIG. 7 is an exploded perspective view of the optical
element holding device in FIG. 6;
[0018] FIG. 8 is a perspective view illustrating an optical element
in an optical element holding device according to a third
embodiment of the present invention;
[0019] FIG. 9 is a perspective view of the optical element in FIG.
8 when seen from a different direction;
[0020] FIG. 10 is a side view illustrating an optical element
holding device according to a fourth embodiment of the present
invention;
[0021] FIG. 11 is a side view illustrating an optical element
holding device according to a fifth embodiment of the present
invention;
[0022] FIG. 12 is a side view illustrating an optical element
holding device according to a sixth embodiment of the present
invention;
[0023] FIG. 13 is a cross-sectional view illustrating an optical
element holding device according to a seventh embodiment of the
present invention;
[0024] FIG. 14 is a flow chart of an exemplary device manufacturing
process;
[0025] FIG. 15 is a detailed flow chart of substrate processing in
FIG. 14 for a semiconductor device;
[0026] FIG. 16 is a cross-sectional view illustrating a
conventional optical element holding device; and
[0027] FIG. 17 is an exploded perspective view of the optical
element holding device in FIG. 16.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] (First Embodiment)
[0029] In the following, a first embodiment of the present
invention will be described with reference to FIGS. 1 to 5.
[0030] In the first embodiment, a so-called step-and-scan type
scanning projection exposure apparatus includes a holding device
which embodies an optical element holding device according to the
present invention for holding an optical element (for example, a
lens, a mirror, or the like) such that its optical axis is oriented
in the horizontal direction or in an oblique direction which
inclines at a predetermined angle with respect to the horizontal
direction, and a projection optical system which embodies in part a
barrel according to the present invention.
[0031] FIG. 1 schematically illustrates the configuration of a
whole exposure apparatus which includes a catadioptric system as a
projection optical system. In FIG. 1, the Z-axis is set in parallel
with a reference optical axis AX of the catadioptric system which
comprises a projection optical system 35; the Y-axis is set in
parallel with the sheet surface of FIG. 1 within a plane
perpendicular to the optical axis AX; and the X-axis is set
perpendicular to the sheet surface, respectively.
[0032] This exposure apparatus 31 includes, for example, an F.sub.2
laser (having an oscillation center wavelength of 157.624 nm) as a
light source 32 for supplying exposure light EL in an ultraviolet
region. The exposure light EL emitted from the light source 32
uniformly illuminates a reticle R formed with a predetermined
pattern thereon through an illumination optical system 33. A light
path between the light source 32 and the illumination optical
system 33 is hermetically sealed in a casing (not shown). Then, the
space from the light source 32 to the optical element closest to
the reticle R within the illumination optical system 33 is replaced
with an inert gas such as a helium gas, nitrogen or the like, which
exhibits a low absorption factor for the exposure light EL, is
maintained substantially in a vacuum state.
[0033] The illumination optical system 33 includes a beam shaping
optical system; a fly-eye lens or a rod lens as an optical
integrator; aperture stops of illumination system disposed on an
exit surface of the fly-eye lens; a reticle blind having an opening
which forms a straight slit extending in a direction perpendicular
to a scanning exposure direction; and a condenser lens for
irradiating the reticle R with exposure light formed in a slit
shape by the reticle blind. The aperture stops includes a circular
aperture stop for normal illumination; an aperture stop for
transformed illumination consisting of a plurality of small
openings eccentric from the optical axis; and a circular aperture
stop for annular illumination. The stops are selectively disposed
on the exit surface of the fly-eye lens.
[0034] The reticle R is held by a reticle holder 34a such that a
pattern surface formed on the reticle R is in parallel with an
XY-plane on a reticle stage 34. The pattern surface of the reticle
R is formed with a pattern which is to be transferred onto a wafer
W. The aforementioned illumination optical system 33 illuminates
the reticle R with a rectangular (slit-shaped) illumination region
which has long sides in the X-direction and short sides in the
Y-direction within the entire pattern region. The reticle stage 34
is two-dimensionally movable along the pattern surface (i.e., the
XY-plane) by the action of a driving system, not shown. The
coordinates at which the reticle stage 34 is positioned can be
found by an interferometer 34c which measures the position of a
mirror 34b disposed on the reticle stage 34, so that the reticle
stage 34 is controlled in terms of the position based on the result
of the measurement.
[0035] The light from the pattern formed on the reticle R is led to
the wafer W, which is a photo-sensitive substrate, through the
catadioptric type projection optical system 35. The wafer W is held
on the wafer stage 36 through a wafer table (wafer holder) 36a.
Then, a pattern image is formed in a rectangular exposure region
having the long sides in the X-direction and the short sides in the
Y-direction on the wafer W, so as to optically correspond to the
rectangular illumination region on the reticle R. The wafer stage
36 is two-dimensionally movable along a wafer surface (i.e., the
XY-plane) by the action of a driving system, not shown. The
coordinates at which the wafer stage 36 is positioned can be found
by an interferometer 36c which measures the position of a mirror
36b disposed on the wafer stage 36 or the wafer holder 36a, so that
the wafer stage 36 is controlled in terms of the position based on
the result of the measurement.
[0036] The illustrated exposure apparatus 31 is configured such
that an air-tight state is held within the projection optical
system 35 between the optical element located closest to the
reticle R and the optical element (lens L1 in this embodiment)
located closest to the wafer W. The projection optical system 35
comprised of the optical element located closest to the reticle R
and the optical element located closest to the wafer W. Then, a gas
within the projection optical system 35 is replaced with an inert
gas such as a helium gas, nitrogen or the like, or maintained
substantially in a vacuum state.
[0037] The reticle R and the reticle stage 34 are disposed on a
narrow light path between the illumination optical system 33 and
the projection optical system 35. These reticle R and the reticle
stage 34 are hermetically sealed in a casing (not shown), and the
casing is filled with an inert gas such as nitrogen, helium gas or
the like, or maintained substantially in a vacuum state.
[0038] The wafer W is disposed on a narrow light path between the
projection optical system 35 and the wafer stage 36. These wafer W,
wafer stage 36 and the like are hermetically sealed in a casing
(not shown), and the casing is filled with an inert gas such as
nitrogen, helium gas or the like, or maintained substantially in a
vacuum state.
[0039] This results in the formation of an atmosphere in which the
exposure light EL is hardly absorbed along the overall light path
from the light source 32 to the wafer W.
[0040] As described above, the illumination region on the reticle R
and the exposure region on the wafer W, defined by the illumination
optical system 33, are in the shape of a rectangle which has the
short sides in the Y-direction. Therefore, the reticle stage 34 and
the wafer stage 36, and hence the reticle R and the wafer W are
moved (scanned) in synchronism in the same direction (i.e., to the
same orientation) in the direction of the short sides of the
rectangular exposure region and illumination region, i.e., the
Y-direction, while the driving system, interferometers 34c, 36 and
the like are used to control the positions of the reticle R and the
wafer W. Consequently, the reticle pattern is scanned on the wafer
W to expose a region having a width equal to the long sides of the
exposure region and having a length corresponding to the amount by
which the wafer W is scanned (amount of movement).
[0041] Next, FIG. 2 is a diagram for describing the basic
configuration of the projection optical system 35 contained in a
barrel 37. All refractive optical element (lens components)
comprising the projection optical system 35 are made of fluorite
(CaF.sub.2 crystals). As illustrated in FIG. 2, the catadioptric
system of the present invention includes a first focusing optical
system 40 of refractive type for forming a first intermediate image
of the pattern on the reticle R disposed on a first plane (physical
plane of the projection optical system). The first focusing optical
system 40 is composed of a group of lenses L1, L2, L3, L4, L5, and
L6.
[0042] A first light path bending mirror 41 is disposed near the
position at which the first intermediate image is formed by the
first focusing optical system 40. When the first intermediate image
is formed by the first focusing optical system 40 at a position
between the first focusing optical system 40 and the first light
path bending mirror 41, the first light path bending mirror 41
deflects light flux from the first intermediate image toward a
second focusing optical system 42. In addition, when the first
intermediate image is formed by the first focusing optical system
40 at a position between the first light path bending mirror 41 and
the second focusing optical system 42, the first light path bending
mirror 41 deflects light flux focused by the first focusing optical
system 40 toward the second focusing optical system 42. The second
focusing optical system 42 has a concave reflective mirror 43, and
a group of lenses 44 composed of at least one minus lens for
forming a second intermediate image (which is an image of the first
intermediate image and a secondary image of the pattern)
substantially equal in size to the first intermediate image near
the position at which the first intermediate image is formed, based
on the light flux from the first intermediate image. These concave
reflective mirror 43 and lens group 44 are vertically disposed such
that their optical axis AX' is oriented in the horizontal
direction. In the following, the lens group 44 is called the
"vertically disposed lens group."
[0043] A second light path bending mirror 45 is disposed near the
position at which the second intermediate image is formed by the
second focusing optical system 42. When the second intermediate
image is formed by the second focusing optical system 42 at a
position between the second focusing optical system 42 and the
second light path bending mirror 45, the second light path bending
mirror 45 deflects light flux from the second intermediate image
toward a third focusing optical system 46. Further, when the second
intermediate image is formed by the second focusing optical system
42 at a position between the second light path bending mirror 45
and the third focusing optical system 46, the second light path
bending mirror 45 deflects light flux focused by the second
focusing optical system 42 toward the third focusing optical system
46. Here, the reflecting surface of the first light path bending
mirror 41 is spatially isolated from the reflecting surface of the
second light path bending mirror 45. In other words, the
configuration is designed such that the light flux reflected by the
first light path bending mirror 41 is not directly led to the
second light path bending mirror 45 while the light flux reflected
by the second light path bending mirror 45 is not directly led to
the first light path bending mirror 41.
[0044] The first light path bending mirror 41 and the second light
path bending mirror 45 may be formed of members independent of each
other, or the first light path bending mirror 41 and the second
light path bending mirror 45 may be simultaneously formed in a
single member.
[0045] The third focusing optical system 46 forms a reduced image
of the pattern on the reticle R (which is an image of the second
intermediate image and a final image of the catadioptric system) on
the wafer W placed on a second plane (image plane of the projection
optical system) based on the light flux from the second
intermediate image. The third focusing optical system 46 is
composed of a group of lenses L7, L8, L9, and L10.
[0046] The barrel 37 includes a first barrel section 52a for
containing the first focusing optical system 40 and the third
focusing optical system 46, and a second barrel section 52b for
containing the second focusing optical system 42.
[0047] Next, detailed description will be provided for the
configuration of an optical element holding device 51 in connection
with FIGS. 3-5, according to the first embodiment for holding the
vertically disposed lens group 44 of the second focusing optical
system 42.
[0048] In that regard, FIG. 3 illustrates a cross-sectional view of
the optical element holding device 51 according to the first
embodiment, FIG. 4 illustrates a side view of the optical element
holding device 51 when seen from the direction of the optical axis
AX' of the vertically disposed lens group 44, and FIG. 5
illustrates an exploded perspective view of the optical element
holding device 51 according to the first embodiment.
[0049] As illustrated in FIGS. 3 to 5, a flange 60a is formed along
the outer peripheral surface of a lens 60 which is an optical
element forming part of the vertically disposed lens group 44. The
flange 60a corresponds to the position at which the lens 60 is
held. The flange 60a includes a plane P1 which includes the center
of gravity Gc of the lens 60 when it is vertically disposed. The
plane P1 is substantially perpendicular to the optical axis AX' of
the lens 60, and extends in the gravity direction. The flange 60a
also includes parallel flange surfaces 60b and 60c at positions
spaced by the same distance from the plane P1.
[0050] The optical element holding device 51 includes a frame 61
which is a coupler coupled to the second barrel 52b; and three
holders 62 disposed on the frame 61 at equal angular intervals.
Thus, the flange 60a of the lens 60 is held in these holders
62.
[0051] Specifically, the frame 61 is formed of a metal material
such as aluminum in an annular shape, and is formed with three
bearing surfaces (see FIG. 5), including the holders 62, formed on
the inner peripheral surface at equal angular intervals. In
correspondence to the respective bearing surfaces 63, three
clamping members 64, comprising the holders 62, are attached on one
side of the frame 61 at equal angular intervals with bolts 66 which
are threaded into screw holes 65 on the frame 61.
[0052] The bolts 66 are fastened to clamp the flange 60a of the
lens 60 between the respective clamping members 64 and the bearing
surfaces 63, thereby holding the lens 60 in the frame 61. In
addition, as the frame 61 is assembled into the horizontal barrel
52 of the barrel 37 in this state, the lens 60 is held with its
optical axis AX' oriented in the horizontal direction.
[0053] In this event, as illustrated in FIG. 3, when the three
holders 62 hold the flange 60a of the lens 60, respectively, the
plane P1 positioned halfway between the flange surfaces 60b and 60c
is arranged in the same direction as the gravity direction Gd
through the center of gravity Gc of the lens 60. This plane P1 is
perpendicular to the optical axis AX' of the lens 60. Thus, unlike
the conventional configuration which causes misregistration between
the plane P1 at an intermediate position of the flange 60a and the
center of gravity Gc of the lens, no moment of rotation will be
produced in the lens 60 due to the gravity acting on the lens 60.
Consequently, the lens 60 is prevented from deformation of the lens
surfaces and resultant impairment of the optical performance
thereof (for example, various aberration such as wave front
aberration and spherical aberration).
[0054] While the first embodiment has been described on the
assumption that the intermediate position exists between the
clamping member 64 and the bearing surfaces 63, i.e., between the
flange surfaces 60b and 60c, the plane P1 may not exist at the
intermediate position between the flanges 60b and 60c. For example,
the plane P1 may be located at a position including the flange
surface 60b of the flange 60a, which is in contact with the
clamping members 64, or the plane P1 may be located at a position
including the flange surface 60c of the flange 60a which is in
contact with the bearing surfaces 63.
[0055] The holding position may be a position including the
clamping members 64 and the bearing surfaces 63 as well as the
position including the flange surfaces 60b and 60c of the flange
60a.
[0056] When the lens 60 is held, the three holders 62 are disposed
at positions rotationally symmetric about the optical axis AX' of
the lens 60 at substantially equal angular intervals along the
periphery of the lens 60, as shown in FIG. 4. In addition, the
three holders 62 are disposed at positions symmetric to a plane P2
which includes the optical axis AX' of the lens 60 and extends in
the gravity direction Gd. In other words, one upper holder 62 is
disposed on the plane P2, while the two remaining holders 62 are
disposed at positions symmetric to the plane P2. In this way, the
lens 60 is stably held without deviation.
[0057] Thus, the first embodiment provides the following
advantages.
[0058] (A) In the optical element holding device 51, the respective
holders 62 hold the flange 60a of the lens 60 such that the plane
P1 included in the holding position passes through the center of
gravity Gc.
[0059] For this reason, the plane P1 included in the holding
position of the holders 62 is set to pass through the center of
gravity Gc of the lens 60 without being biased from the center of
gravity Gc, so that the lens 60 can be stably held without
producing a moment of rotation. It is therefore possible to
restrain deformation of the optical surfaces of the lens 60 due to
the absence of the moment to maintain satisfactory optical
performance.
[0060] (B) In the optical element holding device 51, the three
holders 62 are disposed at positions rotationally symmetric to the
optical axis AX' of the lens 60 at substantially equal angular
intervals along the periphery of the lens 60. Thus, the lens 60 can
be more stably held by the three holders 62 disposed at the
positions rotationally symmetric to the optical axis AX' at
substantially equal angular intervals.
[0061] (C) In the optical element holding device 51, the three
holders 62 are disposed at positions symmetric to the plane P2
which includes the optical axis AX' of the lens 60 and extends in
the gravity direction Gd. Thus, the lens 60 can be more stably held
by the three holders 62 disposed at the positions symmetric to the
plane P2 which includes the optical axis AX' of the lens 60 and
extends in the gravity direction Gd.
[0062] (D) In the exposure apparatus 31, the vertically disposed
lens group 44, which is contained in the second barrel 52b of the
barrel 37 in a vertically disposed configuration, is held by the
optical element holding device 51 which has the foregoing
advantages (A) to (C).
[0063] It is therefore possible to stably hold the vertically
disposed lens group 44 while preventing the occurrence of the
moment. Thus, satisfactory optical performance can be maintained
for the projection optical system 35 to improve an exposure
accuracy. Then, the use of the exposure apparatus 31 permits highly
integrated semiconductor devices to be manufactured in good
yield.
[0064] (Second Embodiment)
[0065] Next, a second embodiment of the present invention will be
described, mainly concentrating on differences from the first
embodiment.
[0066] In the second embodiment, detailed description will be
provided for the configuration of an optical element holding device
69 for holding a concave reflective mirror 43 which is disposed
vertically in the second focusing optical system such that the
optical axis AX' is oriented in the horizontal direction.
[0067] FIG. 6 illustrates a cross-sectional view of the optical
element holding device 69 according to the second embodiment, and
FIG. 7 illustrates an exploded perspective view of the optical
element holding device 69 according to the second embodiment.
[0068] As illustrated in FIGS. 6 and 7, a mirror 70, which is an
optical element forming part of the concave reflective mirror 43,
is formed with a flange 70a on the outer peripheral surface. The
flange 70a includes a plane P1 which includes the center of gravity
Gc of the mirror 70, when the mirror 70 is vertically disposed. The
plane P1 is substantially perpendicular to the optical axis AX' of
the mirror 70 and extends in the gravity direction. The flange 70a
has flange surfaces 70b, 70c parallel with each other at positions
spaced by the same distance from the plane P1.
[0069] The optical element holding device 69 has a frame 71 formed
of a metal material such as aluminum in a disk shape. A circular
recess 71a is formed at the center of one side surface of the frame
71 for containing the mirror 70. Three bearing surfaces 63, which
comprise-holders 62, are formed at equal angular intervals on the
inner peripheral surface of the recess 71a of the frame 71, while
three clamping members 64, which comprise the holders 62, are
attached on one side surface of the frame 71 with bolts 66. The
frame 71 has the other side surface coupled to the barrel 37 by a
predetermined coupling mechanism (bolts or the like).
[0070] Similar to the first embodiment, the respective holders 62
hold the flange 70a of the mirror 70 such that the plane P1
included in the respective holding positions of the respective
holders 62 passes through the center of gravity Gc of the mirror
70. Also, the frame 71 is assembled into the barrel 37 in this
state, thereby holding the mirror 70 such that the optical axis AX'
thereof is oriented substantially in the horizontal direction
(vertically disposed configuration).
[0071] Again, similar to the first embodiment, the respective
holders 62 hold the flange 70a of the mirror 70 such that the plane
P1 included in the respective holding positions of the respective
holders 62 passes through the center of gravity Gc of the mirror
70. Also, the three holders 62 are disposed at positions
rotationally symmetric to the optical axis AX' of the mirror 70 at
substantially equal angular intervals along the periphery of the
mirror 70. Further, out of the three holders 62, the upper holder
62 is disposed on a plane P2 which includes the optical axis AX' of
the mirror 70 and extends in the gravity direction Gd, while the
two remaining holders 62 are disposed at positions symmetric to the
plane P2.
[0072] Accordingly, the second embodiment can also provide
substantially similar advantages to those described in (A) to (C)
for the first embodiment.
[0073] (Third Embodiment)
[0074] Next, a third embodiment of the present invention will be
described, mainly concentrating on differences from the second
embodiment.
[0075] In the third embodiment, as illustrated in FIGS. 8 and 9, a
mirror 70, as an optical element, is made of a ceramic, and is
formed with a flange 70a on the outer peripheral surface. The
flange 70a includes three notches 70b formed on the peripheral
surface at equal angular intervals. A protrusion 70c is formed at
the center of each notch 70b.
[0076] Similar to the second embodiment, three holders 62 each
having a bearing surface 63 and a clamping member 64 are disposed
on a frame 71 of an optical element holding device 69. Then, both
sides of the protrusion 70c is clamped between the clamping member
64 and the bearing surface 63 of each of the holders 62, thereby
holding the mirror 70 within the frame 71. In addition, both sides
of the protrusion 70c in the tangential direction may be clamped
other than both sides of the protrusions 70C clamped by the
clamping members 64 and the bearing surfaces 63.
[0077] Again, similar to the second embodiment, the respective
holders 62 hold the flange 70a of the mirror 70 such that a plane
P1 including respective holding positions of the respective holders
62 passes through the center of gravity Gc of the mirror 70. Also,
the respective holders 62 are disposed at positions rotationally
symmetric to the optical axis AX' of the mirror 70 and at
substantially equal angular intervals. Further, out of the holders
62, the upper holder 62 is disposed on the plane P2, while the two
remaining holders 62 are disposed at positions symmetric to the
plane P2.
[0078] Accordingly, the third embodiment can also provide
substantially similar advantages to those described in (A) to (C)
for the first embodiment.
[0079] (Fourth Embodiment)
[0080] Next, a fourth embodiment of the present invention will be
described, mainly concentrating on differences from the first
embodiment.
[0081] In the fourth embodiment, as illustrated in FIG. 10, out of
three holders 62 of an optical element holding device 51, a lower
holder 62 is disposed on a plane P2 which includes the optical axis
AX' of a lens 60 or a mirror 70 and extends in the gravity
direction Gd. Then, the two remaining holders 62 are disposed at
positions symmetric to the plane P2.
[0082] Accordingly, the fourth embodiment can also provide
substantially similar advantages to those described in (A) to (C)
for the first embodiment.
[0083] (Fifth Embodiment)
[0084] Next, a fifth embodiment of the present invention will be
described, mainly concentrating on differences from the first
embodiment.
[0085] As illustrated in FIG. 11, in an optical element holding
device 51 according to the fifth embodiment, six holders 62 are
disposed at predetermined angular intervals on the periphery of a
lens 60 or a mirror 70. Then, out of the six holders 62, a pair of
upper and lower holders 62 are disposed on a plane P2 which
includes the optical axis AX' of the lens 60 or mirror 70 and
extends in the gravity direction Gd, while the four remaining
holders 62 are disposed at positions symmetric to the plane P2.
[0086] Accordingly, the fifth embodiment can also provide
substantially similar advantages to those described in (A) to (C)
for the first embodiment.
[0087] (Sixth Embodiment) Next, a sixth embodiment of the present
invention will be described, mainly concentrating on differences
from the first embodiment.
[0088] As illustrated in FIG. 12, in an optical element holding
device 51 according to the sixth embodiment, six holders 62 are
likewise disposed at predetermined angular intervals on the
periphery of a lens 60 or a mirror 70. Out of the six holders 62,
three holders 62 each are disposed at positions symmetricaooy6
opposite one another relative to a plane P2 which includes the
optical axis AX' of the lens 60 or mirror 70 and extends in the
gravity direction Gd.
[0089] Accordingly, the sixth embodiment can also provide
substantially similar advantages to those described in (A) to (C)
for the first embodiment.
[0090] (Seventh Embodiment)
[0091] Next, a seventh embodiment of the present invention will be
described, mainly concentrating on differences from the first
embodiment.
[0092] As illustrated in FIG. 13, in the seventh embodiment, a lens
60 is held by holders 62 of an optical element holding device 51,
and assembled into a barrel 37 through a frame 61, wherein the
optical axis AX' of the lens 60 is oriented in an oblique direction
which inclines by a predetermined angle with respect to the
horizontal direction (obliquely disposed configuration).
Specifically, in this state, a plane P1 which is included in
holding positions of the holders 62 and extends in a direction
perpendicular to the optical axis AX' of the lens 60 inclines by
the predetermined angle with respect to the gravity direction Gd
which passes through the center of gravity Gc of the lens 60.
[0093] However, when the gravity direction Gd is along the holding
positions, i.e., between flange surfaces 60b and 60c, the lens 60
can be before prevented from deformation of optical surfaces
thereof than the conventional structure for holding an optical
element. Therefore, in the obliquely disposed configuration, even
if the optical axis AX' of the lens 60 inclines at a large angle
with respect to the horizontal direction, the flange 60a may be
formed such that the gravity direction Gd is between the flange
surfaces 60b and 60c.
[0094] The seventh embodiment may support not only the lens 60 but
also the concave reflective mirror described in the second and
third embodiments.
[0095] The optical element holding device 51 for supporting the
obliquely disposed lens 60 or mirror in the foregoing manner can be
used, for example, in a catadioptric system, as described in
Japanese Laid-Open Patent Publication No. 2000-47114.
[0096] Accordingly, the seventh embodiment can also provide
substantially similar advantages to those described in (A) to (C)
for the first embodiment.
[0097] (Exemplary Modifications)
[0098] While the respective embodiments have illustrated three or
six holders 62 disposed on the periphery of the lens 60 or mirror
70, the number of the holders 62 may be changed to four, five, or
seven or more.
[0099] While in the respective embodiments, the holder 62 comprises
the bearing surface 63 and the clamping member 64, the holder 62
may be modified to hold an optical element using another clamping
mechanism, an adhesive, brazing, or the like.
[0100] In the second embodiment, the mirror 70 is held with its
optical axis AX' oriented in the horizontal direction.
Alternatively, as in the seventh embodiment illustrated in FIG. 13,
the mirror 70 may be held such that its optical axis AX' is
oriented in an oblique direction which inclines at a predetermined
angle with respect to the horizontal direction.
[0101] While the respective embodiments have illustrated each of
the lens 60 and the mirror 70 as optical element, the optical
element may be another optical element such as a parallel flat
plate. In addition, the optical element may be a flat reflective
mirror as well as a concave reflective mirror.
[0102] The optical element holding device 51 according to the
present invention is not limited to a device for holding a
vertically disposed optical element in the projection optical
system 35 of the exposure apparatus 31 in the forgoing embodiments,
but may be embodied in a device for holding a vertically disposed
optical element in another kind of optical system of the exposure
apparatus 31, for example, an illumination optical system. Further,
the present invention may be embodied in a device for holding an
optical element in an optical system of another optical equipment,
for example, a microscope or interferometer.
[0103] Even in the foregoing cases, substantially similar
advantages can be provided as in the respective embodiments
described above.
[0104] The projection optical system 35 of the exposure apparatus
31 is not limited to a catadioptric type, but may be a total
refractive type in which a projection optical system has an optical
axis inclined with respect to the gravity direction.
[0105] The light source 32 is not limited to F2 laser light for
supplying pulsed light at a wavelength of 157 nm, but may be
implemented by a KrF excimer laser for supplying light at a
wavelength of 248 nm, an ArF excimer laser for supplying light at a
wavelength of 193 nm, or an Ar.sub.2 laser for supplying light at a
wavelength of 126 nm. Single wavelength laser light in an infrared
region or in an oscillated visible light region from a DFB
semiconductor laser or a fiber laser may be amplified by a fiber
amplifier doped, for example, with erbium (or both erbium and
ytterbium), and converted to ultraviolet light using a nonlinear
optical crystal, and resulting harmonics may be used.
[0106] The present invention can be applied not only to an exposure
apparatus for manufacturing microdevices such as semiconductor
devices but also to an exposure apparatus for transferring a
circuit pattern from a mother reticle to a glass substrate, a
silicon wafer or the like for manufacturing a reticle or a mask for
use with an optical exposure apparatus, an EUV exposure apparatus,
an X-ray exposure apparatus, and an electron beam exposure
apparatus. Here, an exposure apparatus which uses DUV (deep
ultraviolet) or VUV (vacuum ultraviolet) light or the like
generally employs a transmission type reticle, wherein a reticle
substrate is made of a quartz glass, quartz glass doped with
fluorine, fluorite, magnesium fluoride, crystal, or the like. On
the other hand, a proximity type X-ray exposure apparatus and
electron beam exposure apparatus employ a reflection type mask
(stencil mask and membrane mask), wherein a mask substrate is made
of a silicon wafer or the like.
[0107] Needless to say, the present invention can be applied not
only to exposure apparatus for use in manufacturing semiconductor
devices but also to an exposure apparatus for use in manufacturing
displays including a liquid crystal display (LCD) device for
transferring a device pattern onto a glass plate, an exposure
apparatus for use in manufacturing thin-film magnetic heads for
transferring a device pattern onto a ceramic wafer, and/or an
exposure apparatus for use in manufacturing image pickup devices
such as a CCD.
[0108] While the foregoing embodiments have been described in
connection with a scanning stepper to which the present invention
is applied, the present invention can also be applied to a
step-and-repeat type exposure apparatus which is adapted to
transfer a pattern on a mask onto a substrate, while the mask and
the substrate are kept stationary, and sequentially move the
substrate in steps.
[0109] In the foregoing embodiments, the catadioptric projection
system has a reduction scaling factor for projection. However, not
limited to the reduction scaling factor, the catadioptric
projection system may have an equal or enlargement scaling factor.
For example, for projection at an enlargement scaling factor, light
is entered from the third focusing optical system 46, which forms a
primary image of the mask or reticle R. Then, the second focusing
optical system 42 forms a secondary image, and the first focusing
optical system 40 forms a ternary image (final image) on a
substrate such as a wafer W.
[0110] At least some of a plurality of lenses or mirrors, which
comprise the illumination optical system 33 and the projection
optical system 35, are held by the optical element holding devices
51 and 69 in the respective embodiments. The illumination optical
system 33 and the projection optical system 35 are assembled into
the body of the exposure apparatus 31 and subjected to optical
adjustments. The wafer stage 36 (including the reticle stage 34
when the exposure apparatus is of a scanning type) composed of a
large number of mechanical parts is mounted in the exposure
apparatus 31 with its wires being connected, and a gas supply pipe
is connected for supplying a gas into the light path for the
exposure light EL. After completion of adjustments (electric
adjustments and operational verification) are made, the exposure
apparatus 31 in the embodiment can be manufactured.
[0111] The parts which comprise the optical element holding device
51 are assembled after impurities such as working oil, metal
materials and the like have been removed therefrom through
ultrasonic washing or the like. The exposure apparatus 31 is
preferably manufactured in a clean room which has controlled
temperature, humidity and atmospheric pressure as well as adjusted
cleanness.
[0112] While fluorite has been given as an example of a glass
material in the embodiments, the optical element holding device 51
of the embodiments can also used for holding crystals such as
quartz, lithium fluoride, magnesium fluoride, strontium fluoride,
lithium-calcium-aluminum-fluoride- , and
lithium-strontium-aluminum-fluoride, glass fluoride comprised of
zirconium-barium-lanthanum-aluminum, or modified quartz such as
fluorine doped quartz glass, quartz glass doped with hydrogen in
addition to fluorine, OH-base containing quartz glass, and fluorine
and OH-base containing quartz glass.
[0113] Next, description will be provided for a method of
manufacturing a device using the aforementioned exposure apparatus
31 using lithography.
[0114] FIG. 14 is a flow chart illustrating an exemplary process
for manufacturing a device (a semiconductor chip such as IC, LSI or
the like, a liquid crystal panel, a CCD, a thin-film magnetic head,
and a micromachine). As illustrated in FIG. 14, first, in step S101
(designing step), the device (microdevice) is designed for its
functions and performance (for example, designing of circuits in a
semiconductor device), and a pattern is designed for implementing
the functions. Subsequently, in step S102 (mask manufacturing
step), a mask formed with the designed circuit pattern (reticle R,
photomask, or the like) is manufactured. On the other hand, in step
S103 (substrate manufacturing step), a substrate (wafer W, glass
plate, or the like) is manufactured using a material such as
silicon, glass, or the like.
[0115] Next, in step S104 (substrate processing step), an actual
circuit and the like are formed on the substrate by a lithographic
technique or the like, as described below, using the mask and the
substrate prepared in steps S101 to S103. Next, in step S105
(device assembling step), the device is assembled using the
substrate which has been processed in step S104. This step S105
includes, as required, steps such as dicing, bonding, and packaging
(chip encapsulation).
[0116] Finally, in step S106 (inspection step), the device
fabricated in step S105 is inspected for verification of device
operability, durability, and the like. The device is completed and
shipped out only after the foregoing steps have been completed.
[0117] FIG. 15 illustrates an example of detailed flow in step S104
in FIG. 14, when a semiconductor device is concerned. In FIG. 15,
in step S111 (oxidizing step), the surface of the wafer W
(substrate) is oxidized. In step S112 (CVD step), an insulating
film is formed on the surface of the wafer W. In step S113
(electrode forming step), electrodes are formed on the wafer W
through vapor deposition. In step S114 (ion implanting step), ions
are implanted into the wafer W. Each of the foregoing steps forms
part of pre-processing steps at each stage of wafer processing, and
are selected and performed as required at each stage.
[0118] At each stage of the wafer process, the foregoing
pre-processing steps, when finished, are followed by
post-processing steps in the following manner. In the
post-processing steps, first, in step S115 (resist forming step), a
photo-sensitive material such as a photoresist is applied on the
wafer W. Subsequently, in step S116 (exposing step), the circuit
pattern on the reticle R is transferred onto the wafer W by the
lithography system (exposure apparatus 31) previously described.
Next, in step S117 (developing step), the exposed wafer W is
developed, and in step S118 (etching step), exposed members are
etched away except for those portions in which the resist remains.
Then, in step S119 (resist removing step), the resist is removed as
it is no longer needed after the etching.
[0119] Multiple circuit patterns are formed on the wafer W by
repeating these pre-processing steps and post-processing steps.
[0120] With the use of the device manufacturing apparatus described
above, the aforementioned exposure apparatus 31 used at the
exposure step (step S116) can accomplish improved resolution by the
exposure light EL in the vacuum ultraviolet range, and highly
accurate control for exposure amount. Consequently, it is possible
to produce highly integrated devices having a minimum line width of
approximately 0.1 .mu.m with good yield.
[0121] It should be apparent to those skilled in the art that the
present invention may be embodied in many other specific forms
without departing from the spirit or scope of the invention. The
present examples and embodiments are to be considered as
illustrative and not restrictive and the invention is not to be
limited to the details given herein, but may be modified within the
scope and equivalence of the appended claims.
* * * * *